Study of genetic diseases with neoplastic manifestations and detailed investigation of families at high risk of cancer may help detect environmental and genetic influences in carcinogenesis, especially when appropriate laboratory assays are used. By chart review, the genetic epidemiology of carotid body tumor and Ewing sarcoma was described; of 222 carotid body tumor patients, l0% had bilateral disease, l7% had other primary tumors, and 7% had at least one similarly affected relative. By clinical examination, polymastia was seen in l9% of renal cell carcinoma patients and ll% of testicular cancer patients (compared to 0-3% in control groups). In two families, apparent excesses of lung cancer were attributed in part to smoking, in part to genetic susceptibility (because three tumors followed radiation or chlorambucil use and one family had a new syndrome of birth defects involving bone and teeth). Unusual in vitro radioresponsivity was found in one family with leukemia, one with diverse malignancies and one with the Gardner syndrome. Guest lectures, literature reviews, and committee activities were done to stimulate similar research worldwide.